Yadunandan Dar

Emulsion-based free-radical retrograde-precipitation polymerization

Part I - FRRPP theory.- Calculations to probe FRRPP behavior of PMAA-MAA-Water system.- Closed-form estimation of reactive polymer domain size for FRRPP control.- Molecular weight considerations in FRRPP behavior.- LCST-UCST-based Copolymerization.- Unsteady-State Mathematical Modeling/Computer Simulation of FRRPP Behavior.- Part II - Emulsion FRRPP (EFRRPP).- Initial approach.- Modified approach.- Impact of process parameters on EFRRPP.- Radical-containing polymer emulsions.- Control experiments to test auto-polymerization of PS and BA.- Part III - Supplementary Topics.- Cloudpoint Studies of PMMA-MMA-Pentane Systems.- PMMA-PBA from Emulsion PMMA-MMA-Pentane Systems.- Low-VOC Latex Paints and Coatings.- Oil Spill Control from Emulsion-based FRRPP Foaming Surfactant Systems.- Polymer Modification of VA-AA-based Copolymer Emulsions.- Oil Dispersants from FRRPP-based Surfactants.

Low VOC Paints and Coatings

This section pertains to the implementation of emulsion polymerization of MMA in n-Heptane under conventional precipitation environment (as low as 60°C reactor operating temperature), although there is the likelihood that emulsion particles react at temperature above the lower critical solution temperature (LCST). Even though phase separation below the upper critical solution temperature (UCST) is believed to occur at the start of reaction within emulsion particles, the hour-glass phase envelope of the PMMA–MMA–n-Heptane system has been shown to provide a pathway system temperature to attain higher levels where they could well go above the LCST. The polymerization system is based on a redox initiation formulation, and the formation of block copolymer in emulsion particles is implemented in a two-stage polymerization procedure. Solvent/precipitant is removed through a stripping operation. In order to minimize residual monomer in the system at the end of the two-stage reaction run and solvent/precipitant removal step, a chase initiator solution is admixed into the reactor. Product emulsion is used as a binder for a latex paint formulation, which is applied as a film and tested for various coating properties.

PMMA–PBA from Emulsion from PMMA–MMA–n-Pentane Systems

This section describes the FRRPP-based emulsion method used to generate PMMA radicals in the first-stage semi-batch reactor system.

Closed-Form Estimation of Minimum Reactive Polymer Domain Size for FRRPP Control

This chapter pertains to the derivation of the analytical expression for estimation of the minimum reactive polymer-rich domain size for the occurrence of a flat temperature profile in FRRPP systems, under quasi-steady-state conditions. The method assumes a cut-off value of −1,000 for \( C\tilde{n} \), and it is based on temperature dependency of the product of the monomer and polymer composition in the polymer-rich domains. With the derived approximate equation, the resulting minimum polymer-rich domain sizes for FRRPP control are obtained for the PS–S–Ether and PMAA–MAA–Water systems. Finally, the resulting analytical expressions explain why asymptotic conversions in FRRPP systems can be relatively low if good radical trapping is realized in the system.

Radical-Containing Polymer Emulsions

This chapter describes the study of the radical-containing polymer-in-water dispersions obtained using the techniques described in the previous chapter. The studies include verification of the presence of radicals in the system through theoretical estimation. Some of the concepts and data presented here are adapted from Caneba and Dar (2002), Dar and Caneba (2001), Dar et al. (2003), and Caneba et al. (2002).

Oil Dispersants from FRRPP-Based Surfactants

The use of Corexit® to disperse oil that was spilled from the BP Deepwater Horizon drilling platform off the Gulf of Mexico just a few months ago has been quite controversial, due to the presence of more aggressive t-butanol and/or hydrocarbon carrier fluids in the formulations. There is a continuing search for more environmentally responsible oil dispersant formulations, since oil spills from offshore platforms are expected to continue to occur in the future. A tabulation of various dispersants registered in the USEPA website (http://www.epa.gov), their effectiveness and toxicities is shown in Table 18.1.

Impact of Process Parameters on EFRRPP

The ability to deliver controlled architecture copolymers from FRRPP in an emulsion form requires a working knowledge of the stabilization of emulsions containing several components through the choice of suitable surfactant package and emulsification conditions. This chapter describes work that was done to make complex emulsions that included polymer in oil-in-water dispersions that were ultimately modified to polymer-in-water emulsions, as well as the manipulation of preemulsified systems that provided stable final products. Some additional details are provided in Dar and Caneba (2002, 2004).

Oil Spill Control from Emulsion-Based FRRPP Foaming Surfactant Systems

The 2010 rig disaster from the Deepwater Horizon/Macondo well off the Gulf of Mexico and its aftermath has rekindled the debate on deepwater drilling and offshore oil exploration in the United States. The heavy use of dispersants from the ill-fated well has been known, and it has been documented that underwater oil plumes are lurking beneath the water surface (Thibodeaux et al. 2011). There is a need to understand the processes involved in the formation of these plumes, and how to address their lingering presence.

LCST–UCST-Based Copolymerizations

It was shown in Chap. 3 that a polymerization system can start as a conventional precipitation system and end as an FRRPP system, especially if the phase diagram exhibits an hourglass-shaped phase envelope at relatively high polymer molecular weight. This sets up the arguments for other types of shifts from UCST- and LCST-based chain polymerizations, especially in cases wherein multiple monomers are involved. The analysis here will be made for two monomers (copolymerizations), but can be easily extended to multiple monomers. Operationally, it should be emphasized that this is basically a one-pot polymerization methodology, which can be extended to semibatch reactant introduction into the reactor.

Control Experiments to Test Autopolymerization of styrene and n-butyl acrylate

It is important to rule out the possibility that stage II monomers can homopolymerize under the reaction conditions to somehow lead to the effect observed in the experiments in Chap. 10. The presence of significant levels of homopolymerization could also lead to the possibility of chain transfer and radical initiation on the polymer backbone, which could still lead to potentially similar effects as would be produced by trapped polymer radicals.